The present invention relates to an ink set for ink jet, an ink jet coloring process using thereof, and a colored product for outdoor obtained by the process. More specifically, the present invention relates to an ink set for ink jet superior in warm color representation and weather resistance, an ink jet coloring process and a colored product for outdoor.
Although ink jet printing has been conventionally studied as a coloring process for various materials, excellent weather resistance capable of corresponding to all natural conditions is required in case that the material is employed for outdoor use. The weather resistance is property in which an image printed on a material is retained without change in color and color degradation for a fixed period even if it is exposed to heat, light and water, and various trials have been carried out for an ink jet ink for printed articles used out of doors.
Organic pigments more superior in weather resistance than a dye are proposed as a coloring agent for an ink jet ink (for example, Japanese Unexamined Patent Publication No. 2004-107633 and Japanese Unexamined Patent Publication No. 2004-107637). However, since they are exposed to sunlight for a long period in outdoor use, it is difficult to prevent color degradation when an organic pigment is used. In case of outdoor use, there has been required weather resistance in which color degradation occurs hardly for 5 to 10 years out of doors usually and after exposure to heat, light and water.
Accordingly, an ink for ink jet using an inorganic pigment superior in weather resistance than an organic pigment as a coloring agent is proposed (for example, Japanese Unexamined Patent Publication No. 2001-055530). However, although the inorganic pigment is superior in weather resistance, it is often inferior in coloring ability and sharpness in comparison with the organic pigment. Although there are those having coloring ability and sharpness even among the inorganic pigments, these include harmful substances such as mercury, lead, cadmium and chromium and should not be used considering influence to a human body and environments.
On the other hand, warm color representation such as brick tone and woodgrain has been required in building materials such as a siding material used out of doors; therefore, colors such as orange, brown and brick red color are often used. In the warm color representation, dense orange color is particularly required for abundant density representation. However, even if a yellow inorganic pigment and a red inorganic pigment are used, there has been a problem that orange color with chroma saturation and density tone is not obtained.
Thus, it is status quo that there has not been developed yet an ink set for ink jet capable of providing printed articles superior in weather resistance for a material for outdoor use such as a siding material and capable of providing color representation in brick tone and woodgrain and in particular, capable of providing warm color representation such as orange color with chroma saturation and density tone.